Goods and other items may be tracked and identified using an RFID system. An RFID system includes a tag and a reader. The tag is a small transponder typically placed on an item to be tracked. The reader, sometimes referred to as an interrogator, includes a transceiver and an antenna. The antenna emits electromagnetic (EM) waves generated by the transceiver, which, when received by tag, activates the tag. Once the tag activates, it communicates using radio waves back to reader, thereby identifying the item to which it is attached.
There are three basic types of RFID tags. A beam-powered tag is a passive device which receives energy required for operation from EM waves generated by the reader. The beam powered tag rectifies an EM field and creates a change in reflectivity of the field which is reflected to and read by the reader. This is commonly referred to as continuous wave backscattering. A battery-powered semi-passive tag also receives and reflects EM waves from the reader; however a battery powers the tag independent of receiving power from the reader. An active tag actively transmits EM waves which are then received by the reader.
Many applications of RFID systems demand inexpensive tags. High volume manufacturing methods are employed to reduce the cost of conventional tags. These manufacturing methods often provide further economy by using densely packed webs in roll-to-roll processes. Densely packed webs reduce the quantity of web material consumed, and thus the cost of the end product.
In some instances, high density webs are directly at odds with tag performance. An antenna web is a clear example of the tradeoff between cost and performance. In general, an antenna with more area is more easily adapted to multi-axis capabilities than one that has a relatively small area. That is to say, conventional techniques have yielded either a less expensive antenna or a larger antenna with superior omni-directional performance. This tradeoff is often made difficult because omni-directional performance happens to be critical in many RFID applications where relative orientation of a tag to a reader is unpredictable.
From the above it is seen that techniques for inexpensive tags with improved multi-axis performance are desired.